Caption: Genetic mutations and cancer. Artwork showing the genetic basis of the formation of a cancerous tumour. Chromsomes (far left) contain genes that help to suppress tumour formation. When exposed to a carcinogenic, or toxic substance (yellow warning symbol), these chromosomes are damaged. The middle diagram shows a damaged cell replicating to form cancerous cells. The final diagram shows the cancerous cells multiplying to form a tumour within a block of tissue.